The fast growing biotechnological industry is generating a new kind of pollution problem from solid residue from microorganism biomass. The microorganisms have been using as single cell factory, such as brewer yeast to produce ethanol via fermentation process where ethanol is used as alternative energy in the automotive industry wherein after purification of ethanol, yeast remains as by-product or waste.
Similarly, microalgae which are conventionally used in food production and food additive industries have in recent years come into the spotlight of the biofuel industry since several species are capable of producing oils and lipids. Microalgae are excellent candidates for fuel production because of their combined advantages of high-photosynthetic efficiency, biomass production and faster growth, as compared to other energy crops. Microalgae are grown in large-scale photobioreactors for the industrial-scale production of biofuel, consequently a huge amount of microalgae biomass remains after oil extraction process. After completion of the production processes, the discarded microorganisms remain as large amount of solid waste resulting in a new kind of pollution problem as aforementioned. To solve this pollution problem, there is a need to find a better way for disposal or add economic values of these microorganism wastes.
One of the common practices for disposal of the microbial solid waste by the biotechnology industry is to dispose tons of such waste as a landfill. Other several solutions have also been proposed. For instance, Shiho et. al., (2011) suggested that the waste of microalgae Botryococcus biomass can be used as heat generator in which the combustion heat of the solid component was observed experimentally and was found to be 31-34 MJ/kg with 3% moisture content. However, drying process before gaining that very low moisture content might be costly and inefficient. In another example, the yeast solid waste from bio-ethanol industry has been utilized as feed supplements. However, its consumption is very limited due to difficulties in quality control of yeast solid waste. Hence, the proposed application cannot be a sustainable solution to eliminate large amount of yeast biomass.
Another proposed solution to this problem is incorporating the biomass with plastics. U.S. Pat. No. 5,346,929 disclosed a method of preparation of resin made from mixture of synthetic biodegradable polymer and starch from fungi Aspergillus but the method/process of resin production including its advantage was unclear. U.S. Pat. No. 8,026,301 teaches the polymer composition comprising a complex of petroleum-based resin such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride and cellulose, chemical based-nitrogen source, natural nutrient from blue-green algae or yeast in order to increase their biodegradability.
However, the incorporation of the biomass with plastics requires further supplementation of the additives, such as compatibility agents to maintain the polymer properties and their compatibilities otherwise the amount of biomass added in plastics would be very limited. Moreover, none of known methods teach or suggest a worthwhile technique to enhance the use of biomass not only to improve the biodegradability of biodegradable polymers but also to enhance properties, such as viscosity or compatibility, of biodegradable polymer compositions which are very vital in the production of biodegradable plastics.
Biodegradable plastics claim to be environmentally friendly. They can be produced from plants and its derivatives or other several renewable sources. Biodegradable plastics are plastics which are capable of degradation when they are attacked by microorganisms in natural or artificial conditions whereby the molar mass of degraded biodegradable plastics are reduced and hence can be transported into the microorganisms and fed into the appropriate metabolic pathways. As a result, the end-products of these metabolic processes include water and carbon dioxide (CO2) together with newly producing biomass. A good example of biodegradable plastic is polylactide or poly Lactic acid (PLA). PLA can be produced by polymerization of bacterial fermented lactic acid and is claimed to be free from using of non-renewable source and to solve the environment problems. Therefore, PLA has rapidly become a focus of attention as a material alternative to existing plastics or fibers that are made from petroleum route. Another example biodegradable plastic is Poly (butylene Succinate) (PBS).
Indeed, currently available biodegradable resins require the addition of polymer additives such as color concentrate or pigment to enable their applications. Attempts have been made to process color concentrate on standard equipment and using known technologies in the plastic industry. For example, U.S. Pat. No. 8,133,558 discloses a method for producing PLA blown film composed of 1-20% of Titanium oxide (TiO2) to develop its special colors. U.S. Pat. No. 7,273,896 discloses a method to visualize medical biomaterials from polysaccharide by using Fluorescein. U.S. Pat. No. 7,687,568 discloses a process of producing a polyester colorant concentrate by using carbon black pigment, Monoazo pigment, Disazo pigment, Phthalocyanine pigment, Anthraquinone pigment or Quinacridone pigment.
None of the above mentioned patents teach or suggest a method of production of biodegradable product which is made completely of bio-based materials. All of the colorant additive materials described in those patents are derived from non-renewable resources which cause much more serious environment problems because those molecules, such as fluorecein, are toxic to human as they disperse into the surrounding once the biodegradation process of the resin has occurred.
On the other hand, natural colorants wherein the main components or materials derived from natural products and/or their by-products offer an effective solution in eliminating or diminishing pollution on the earth. For example, U.S. Pat. No. 5,205,863 discloses a method for producing bio-plastic from starch acetate (starch acetate polymer) using 1% of red natural pigment from berry fruit as colorant additives. However, this method generates at least two new problems. First, the above production faces difficulties in controlling quality of raw material, especially controlling the color of fruit, because color in the fruits depends on climate and physical parameters such as light intensity, water supply, nutrient in soils, etc. Second, the security of raw material becomes to be issue because huge amount of those fruits are required and this may directly affect the human food supply. Therefore, the commercial production according to this method is almost impossible.